1. Field of the Invention
This invention relates to a vehicular left/right drive torque adjusting apparatus suitable for use in the distribution of drive torque to the left and right wheels in a four-wheel-drive or two-wheel-drive automotive vehicle.
2. Description of the Related Art
Recent years have seen major developments in four-wheel-drive (hereinafter called "4WD") automotive vehicles, including a variety for full-time 4WD automotive vehicles where improvements include positive adjustment of the division of torque (drive torque) between front and rear wheels.
When two members which are rotating at different rotational speeds are coupled together, the difference in their rotational speeds is generally reduced and torque is usually transferred from the side of the member rotating at the higher speed to the side of the member rotating at the lower speed. Differential-limiting, front/rear torque distribution apparatuses making use of these characteristics have been proposed.
Distribution of torque between the front and rear wheels can be adjusted, for example, by providing a center differential, which is arranged between the front wheels and the rear wheels, with a differential limiting mechanism of the frictional engagement type to limit differential motion (a difference in rotational speed) between the front and rear wheels and controlling the state of engagement of the differential limiting mechanism. As the differential limiting mechanism, a hydraulic multi-plate clutch, use of an electromagnetic clutch or the like can be considered. When a hydraulic multi-plate clutch is used, the state of engagement of the hydraulic multi-plate clutch, that is, of the differential limiting mechanism can be controlled by adjusting the position of a hydraulic pressure control valve in accordance with a computer or the like.
Taking in a broad sense a mechanism for distributing torque to left and right wheels in an automotive vehicle, on the other hand, it is considered to include conventional normal differentials as well as LSDs (limited slip differentials) including those of the electronic control type. They however do not positively adjust the distribution of torque, so that they cannot distribute torque between left and right wheels as desired.
Therefore it is also desired to develop an apparatus capable of adjusting the distribution of torque between the left and right wheels in addition to an apparatus for permitting adjustment of the distribution of torque between the front and rear wheels. In this case, the left/right torque distribution adjusting apparatus is intended for use in the adjustment of torque distribution not only between the left and right driving wheels in a 4WD vehicle but also between the left and right driving wheels in a 2WD vehicle such as a front wheel drive vehicle or a rear wheel drive vehicle.
Incidentally, it is desired for a torque distribution mechanism that the distribution of torque can be effected as desired without inducing any large torque loss or energy loss. It is also desired to reduce the size and weight of the mechanism as much as possible.